The present invention relates to an air pollution preventing device in an internal combustion engine in which discharge of blow-by gas in a crank chamber to the atmosphere is prevented, and exhaust gas is returned to a combustion chamber to restrain release of polluting substance contained in burned gas.
An air pollution preventing device in which blow-by gas and exhaust gas are led to a suction chamber provided on a top of an internal combustion engine to be mixed with suction air and supplied to a combustion chamber, has been known as shown in Japanese Laid-Open Patent Publication Hei 5-99079.
In this air pollution preventing device, a blow-gas passage and an exhaust gas return passage leading to the suction chamber are arranged on a straight line crossing a plurality of parallel manifold suction passages. Ends of the blow-by gas passage and the exhaust gas return passage are opened in the suction chamber facing each other, and a partition wall hanging from a top wall of the suction chamber is positioned between the openings of the blow-by gas passage and the exhaust gas return passage. Therefore, blow-by gas entering the suction chamber from the blow-by gas passage and return exhaust gas entering the suction chamber from the exhaust gas return passage are directed downward by the partition wall to be mixed with each other and supplied to a manifold suction passage opening to the suction chamber.
In the above-mentioned air pollution preventing device, since return exhaust gas having not been cooled enough comes into contact with blow-by gas not pre-cooled yet, oil mists and the like in the blow-by gas accumulate just beneath the partition wall as a sludge to lower flow rate of the return exhaust gas.
Since the confluence of the return exhaust gas and the blow-by gas is positioned near one manifold suction passage among a plurality of manifold suction passages, temperatures and flow rates of the return exhaust gases and the blow-by gases entering respective manifold suction passages are different from one another.
In order to cope with such problems and improve the customary air pollution preventing device, the present invention provides an air pollution preventing device in an internal combustion engine having a blow-by gas treatment chamber unit and an exhaust gas return chamber unit placed one upon another on a suction manifold. The blow-by gas treatment chamber unit has a blow-by gas chamber communicating with a crank chamber through a blow-by gas passage and a blow-by gas passage leading from the blow-by gas chamber to a suction passage, and the exhaust gas return chamber unit has an exhaust gas return chamber communicating with an exhaust passage through an exhaust gas return passage and an exhaust gas return passage leading from the exhaust gas return chamber to a suction passage.
According to this invention, return exhaust gas flowing in the exhaust gas return chamber and the exhaust return passage leading from the exhaust gas return chamber to the suction passage is cooled by atmospheric air coming into contact with an outer surface of the exhaust gas return chamber unit and also by the blow-by gas treatment chamber unit coming into contact with the exhaust gas return chamber unit, then mixed with the blow-by gas together with suction air flowing in the suction passage. As the result, sludge resulting from reaction of oil mist within the blow-by gas is reduced greatly.
Since the blow-by gas treatment chamber unit and the exhaust gas return chamber unit are placed one upon another on the suction manifold, the internal combustion engine can be miniaturized as a whole.
The exhaust gas return passage between the exhaust gas return chamber and the exhaust passage may have an exhaust gas return valve, at least a portion of the exhaust gas return passage on down stream side of the exhaust gas return valve may be formed by a corrugated pipe, and an outer wall of the exhaust gas return chamber may be provided with cooling fins. The return exhaust gas is cooled by the corrugated pipe and the cooling fins more efficiently.
Every suction passages of the suction manifold may communicate with the blow-by gas chamber and the exhaust gas return chamber through respective blow-by gas passages and exhaust gas return passages. Cooling of the return exhaust gas is promoted more, the return exhaust gas is uniformly supplied to combustion chambers of the internal combustion engine through the suction passages, combustions in the combustion chambers are equalized, and discharge of polluting substance is restrained more effectively.